Alloy



Patented June 24, 1930 UNITED STATES PATENT OFFICE CHARLES PACK, OF BROOKLYN, new YORK, AND JOSEPH 0. FOX, 01; TOLEDO, OHIO, ASSIGNORS T DOEI-ILER DIE-CASTING 00., A CORPORATION on NEW YORK ALLOY No Drawing.

Our invention relates to alloys, and particularly to zinc base alloys having means for retarding the aging thereof.

In the development of the art of alloying 5 of metals, it has been found desirable to prepare a number of zinc base alloys having characteristics adapting them to various purposes, and especially to the production of castings in metal molds or dies. Zinc alone, in the pure form, solidifies from the molten state in relatively large crystals, and tends to be rather brittle and of rather low strength and therefore unsatisfactory for castings. Many attempts have been made to alloy other metals with the zinc to produce a stronger more satisfactory materiaL' In some cases the added alloy metals have produced desirable results. In many cases however the desirable results have been accompanied by. undesirable phenomena of various sorts, some of which manifest themselves only after the passage of considerable time. These effects are known as aging, and they may take a number of forms depending upon the type and quantity of the alloying metal.

In the production of zinc castings, substantial gains in strength have been obtained by the inclusion of various proportions of aluminum in the alloy with, or without, other common metals. An alloy of zinc with a small percentage of aluminum manifests a greatly increased strength, has a finer grain, and is much more satisfactory for casting processes, particularly die casting. The inclusion of the aluminum, however, develops a very serious difiiculty, because of the tendency of the alloy to disintegrate'by a process of swelling or aging, with the passage of tion of other valuable properties.

time. This phenomenon is particularly no- Application filed August 8, 1927. Serial No. 211,623.

the'tendency to swell, and if added in more than small proportions may bring other difficulties into prominence. These may be undue brittleness when cold, or may be hot shortness, etc. Various other metals have been added in attempts to overcome some of these difliculties, but with only small degrees of success.

The alloy of our invention largely overcomes these difliculties by the inclusion of lithium with the metals, which may be present in small to moderate amounts. The alloy of our invention, containing lithium, may be made up in a. number of modifications, particularly with the zinc base, and it may desirably include zinc and aluminum as well as lithium. To this combination of elements, other metals may be added for the produc These may be copper, nickel and other usual metals. When so made up the resulting alloys are of the desired high strength andfine grain, and the change of physical state and characteristics as well as the disintegration of the material by the, effect known as aging, is very much retarded or entirely removed. Alloys made according to the composition of our invention may stand substantially unchanged under conditions otherwise seriously harmful to zinc base alloys for very long times,without injury. Furthermore, the addition of lithium in substantial quantities does not produce the brittleness characteris Y tic of other substances which retard the aging and accordingly it brings no other ditficulties with it when included in an alloy. We are thus enabled to produce an alloy, having a zinc base, which is of substantially increased strength, which is free from brittleness, and which is resistant to aging and to other destructive agencies.

A suitable embodiment of the alloy of our invention may consist of an alloy containing approximately 90.55% of zinc, 4% 'of copper, 0.25% of nickel, 5% of aluminum, and 0.2% of lithium. The alloy may be made by any suitable method of foundry practice which will produce a material containing the desired constituents. The process may conveniently consist in a melting of the zinc, and the adding thereto of the desired proportion of copper and nickel, desirably in the form of chips or turnings, in which relatively little loss occurs in the melting operation, thereafter adding to the melt, the aluminum and lithium in the desired quantities and in suitable excess to allow for melting losses and still have present in the completed alloy the desired proportion of each. The alloy may desirably be carefully mixed and skimmed in accordance with customary foundry practice after which it may be poured in the usual way, according to the purpose for which it is to be used.

The allow, as so produced, has a desirably high electro-positive potential, but the added electro-negative metals are included in such condition that theireffect is largely masked and the material isin consequence very resistant to corrosion. Likewise the crystals are broken up into desirably small dimensions, with a very strong intercrystalline eutectic alloy, and the material is accordingly of very high physical strength.

The eutectic alloy being strong, the material likewise has excellent wear resisting properties. The inclusion of the relatively high percentage of lithium causes the alloy to be entirely resistant to swelling, and the presence of the nickel and copper further improves the physical properties.

Substantial changes are possible in the composition of the alloy of our invention from the embodiment just disclosed. Desirable results may be obtained with a percentage of aluminum as low as 1%, and also over the range of composition from 1% to 15% of aluminum or higher according to the requirements imposed upon the alloy. Likewise the proportion of copper may be varied from a fraction of 1% to approximately 10% and the percentage of nickel may likewise be varied over a reasonably wide range. Alternatively the copper and nickel may be entirely omitted. The percentage of lithium may. advantageously be varied from an amount as low as 0.01%-, to an amount as hlgh as several per cent, depending upon the purpose for which the alloy is intended.

Various proportions of other metals may also be added for the production of advantageous results. Substantial gains in strength and durability may be obtained in the alloy by the inclusion of both, lithium and magnesium, and other metals may desirably be utilized in cooperation with the lithlum.

Lithium likewise produces advantageous results when included in alloys having another base than zinc. For instance, in the inclusion of lithium in. an aluminum base alby, with orwithout the inclusion of proportions of copper and nickel, or of copper, nickel and magnesium, produces further additional and valuable gains, in crystal structure, strength of eutectic alloy, freedom from aging, ease of casting and other desirable properties.

By this means we have produced a group shall be imposed upon the claims hereafter presented as are required by the prior art or indicated therein.

We claim as our invention:

1. A zinc base alloy comprising zinc in excess of aluminum, and lithium in appreciable amount less than 5%.

2. A zinc base alloy containing zinc in excess of 75% in combination with aluminum,

copper and lithium the latter being in appreciable amount less than 5%.

3. A zinc base alloy containing zinc in excess of 75% in combination with aluminum copper, nickel and lithium the latter being in ap reciable amount less than 5%.

4. n alloy comprising in combination, a zinc base in excess of 75%, aluminum Within the range of 1 to 15%, copper within the range of 1 to 10%, nickel less than 5%, and lithium in appreciable amount less than 5%.

5. An alloy comprising in combination, a zinc base in excess of 75%, aluminum within the range of 1 to 15%, copper within the range of 1 to 10%, and lithium in appreciable amount less than 5%.

6. An alloy comprising in combination, a zinc base in excess of 75%, aluminum within the range of 1 to 15 and lithium in appreciable amount less than 5%.

In witness whereof, we hereunto subscribe our signatures.

' CHARLES PACK. JOSEPH C. FOX. 

